1. Field of the Invention
The invention relates to video and other reflective-photonic inspection systems for non-destructive internal inspection of power generation machines, such as combustion or steam turbine engines, generators, and other plant equipment for power generation. More particularly, the invention relates to video/camera inspection systems having self-supporting and shape-retaining elongate deformable deployment tethers and a camera head coupled to the deployment tether distal end, for capturing images of internal areas of interest within power generation equipment. The deployment tether is bendable, for insertion through cavities of the power generation machine and orientation of the camera head field of view on the internal area of interest within the machine. The deployment tether is capable of being deformed repeatedly for inspection of different areas of interest within the same machine or in different machines.
2. Description of the Prior Art
Power generation machinery, such as steam or gas turbine engines or generators, are often operated continuously with scheduled inspection and maintenance periods, at which time the machinery is taken off line and shut down. By way of example, a gas turbine engine often will be operated to generate power continuously for approximately 4000 hours, thereupon it is taken off line for routine maintenance, inspection, and repair of any components identified during inspection. Taking a gas turbine engine off line and eventually shutting it down completely for scheduled maintenance is a multi-day project. Some turbine components, such as the turbine rotor section, are operated at temperatures exceeding 1000° C. (1832° F.). The turbine requires 48-72 hours of cooling time to achieve ambient temperature before complete shutdown in order to reduce likelihood of component warping or other deformation. During the shutdown phase the turbine rotor rotational speed is spooled down from operating speed of approximately 3600 RPM to a speed of approximately 120 RPM or less in “turning gear mode” where the rotor is externally driven by an auxiliary drive motor, in order to reduce likelihood of rotor warping. Other turbine components, such as the turbine housing, are also cooled slowly to ambient temperature.
Once the turbine is cooled to ambient temperature over the course of up to approximately 72 hours internal components of the now static turbine can be inspected with optical camera inspection systems. Known optical camera inspection systems employ rigid or flexible optical bore scopes that are inserted into inspection ports located about the turbine periphery. The bore scope is manually positioned so that its field of view encompasses an area of interest within the turbine, such as one or more vanes or blades, combustor baskets, etc. A camera optically coupled to the bore scope captures images of objects of interest within the field of view for remote visualization and archiving (if desired) by an inspector. Rigid tube borescopes are not insertable in twisting or tightly confined cavities within power generation machinery. Flexible tether borescopes are not self-supporting, so the camera field of view stability is disrupted by inadvertent tether movement, such as if the tether inadvertently slips during video inspection. Flexible tether borescopes inadvertently contact internal surfaces within power generation machinery as they are maneuvered through internal machinery passages, risking potential damage to relatively brittle and fragile surfaces, such as thermal barrier coatings on turbine engine blades, vanes or combustor transitions.
Complete turbine inspection requires multiple manual relative repositioning sequences between the camera inspection system viewing port and areas of interest within the turbine by a human inspector. In many field service applications it is also desirable to gather multiple types of visual inspection data, including dimensional and/or surface profile data and/or a general video record of power generation machine internal components during a single pre-teardown inspection cycle. Each type of non-destructive evaluation visual inspection requires a different type of bore scope device/system to perform each specific type of inspection.